The objectives of this CAREER project are: (1) to gain fundamental understanding of the nucleation of dislocations in crystalline materials under near-failure stresses, (2) to apply this understanding broadly to issues concerning the mechanical properties and structural integrity of materials, and (3) to integrate the activities in the above research areas with the education of undergraduate and graduate students. The research component of the project investigates an issue of fundamental importance to mechanical properties and structural integrity of crystalline materials, the nucleation of dislocations under high stresses. The research focuses on the experimental validation and improvement of the latest autocatalytic nucleation model. The objective of achieving fundamental understanding is accomplished through critical experiments to probe in situ the formation of dislocations in initially dislocation-free crystals subjected to dynamic loading and heating and through analytical and numerical formulations of the autocatalytic nucleation mechanism. The following tasks are performed: (1) Experimental techniques based on electrical resistivity, synchrotron X-ray diffraction and reflection electron microscopy for probing in situ the formation and evolution of dislocations in crystalline materials; (2) In situ probing techniques to examine single crystal specimens that are initially free, or effectively free, of dislocations and are subjected to dynamic heating and straining; (3) Models of the collective, autocatalytic nucleation of dislocation loops with analytical and numerical methods; and (4) Application of the experimental and theoretical research to materials properties and issues that are defect-sensitive and involve locally concentrated stresses. %%% The CAREER project includes developing an industrially oriented course on materials selection to cater to the need of non-materials engineering students, for both on-campus students and off-site students at industrial companies and structuring the course for distance learning through Internet technologies. ***
